Do you have colored fabric strips 5" or 6" wide sewn onto the foot and leech of your sail? When tightly rolled up and furled, is that color pretty well unbroken all the way up your sail? If so, then you have UV protectant Sunbrella material sewn on, and it will protect your sail.
If you don't have this, and you have a spare jib halyard, then you should definitely consider buying a jib sock.
If you have a CDI or other furler that has a foil that runs up the forestay, and the sail is attached to this foil (plastic or aluminum, doesn't matter) then the furling system probably has its own halyard to hoist the jib up the foil, and you have an unused jib halyard.
If you have a wire luff furler, such that the sail winds around its own luff, with no foil, then it's quite likely that your jib halyard is holding everything up with a swivel at the top to allow the sail to furl. In this case, one hopes for an unused spinnaker halyard to use to hoist the jib sock up the furled sail. Or one adds a halyard for the sock.
The sock itself is a sleeve with a zipper down the whole length, which allows you to zipper over the furled jib at the same time the sock is hoisted with the halyard.
Does any of this make sense and help?